The present invention is in a separator for an alkaline battery and more particularly in a separator of a non-woven fabric of polyamide fibers.
Conventionally non-woven fabrics formed from nylon 6 and nylon 66 and such non-woven fabrics of polyolefin fibers have been used for separators in alkaline batteries. The separators from the non-woven fabric of nylon 6 and nylon 66 have excellent electrolyte retainability and discharge capacity, and thus can be used favorably for a high discharge rate. However, these fabrics have inferior alkali resistance at high temperature and inferior oxidation resistance. A disadvantage of the conventional polyamide separator is that sulfate and carbonate radicals are generated by fiber decomposition when such fibers are used in an alkaline battery. The battery life is thus shortened.
The separators of non-woven fabric from polyolefin fibers have excellent alkali resistance and oxidation resistance. A disadvantage of the polyolefin separator is they have inferior electrolyte retainability. Such separators leak in a short time when used at high discharge rates.
Various modifications have been tried to eliminate these disadvantages. Non-woven fabric comprising polyolefin fibers which are natively excellent in alkali resistance and oxidation resistance have been subjected to hydrophilic treatment with a surface active agent. Micro-fine fibers have been used as the polyolefin fibers practically used to increase electrolyte retainability. However, such a modification is only temporarily effective or insufficient for use at a high discharge rate due to the inherent hydrophobic property of polyolefin fibers.
Blends of nylon 6 or nylon 66 with polyolefin fibers in a prescribed proportion have been tried to satisfy both electrolyte retainability and alkali resistance/oxidation resistance requirements. However, since nylon 6 and nylon 66 are selectively deteriorated by alkaline electrolyte, any only temporary effectiveness can be achieved.
An object of the present invention is to obtain a separator with excellent electrolyte retainability and having improved alkali resistance and oxidation resistance at high temperature.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.